SLEEP AND ITS REGULATION. 413 



tion which is most natural and best suited to invite the least disturb- 

 ance of the functions of the great organs. To use the analogy of 

 the four-footed animals, and by such facts we can secure the safest 

 guidance, the best position is on the abdomen or nearly so. Habits 

 may, and do, vitiate our instincts here as elsewhere, and we can ac- 

 custom ourselves to many departures from natural and advisable 

 operations. This is especially forceful while in vigorous health, but 

 we are speaking here of securing the best rest with the least tax upon 

 our organism, hence it is well to determine those means which are 

 normal, and employ them. The body should lie as nearly as possible 

 on a level, head and feet as well as body, on the side inclined toward 

 the abdomen, adjusting arms and legs in such a fashion as shall not 

 permit undue pressure upon nerves and bloodvessels, direct or indirect. 



To lie on the back is objectionable for the reason that long con- 

 tinued pressure on the tissues adjacent to the vertebral column, which 

 are innervated by the posterior primary divisions of the spinal nerves, 

 exerts a continued irritation through vasomotor connections to the 

 viscera, disturbing the circulation in the segments. Here are the cell 

 bodies of the vasomotor nerves, which thence pass to the organs and 

 beyond parts, thereby governing function. Thus, dilatation is induced 

 and maintained in the blood vessels of the viscera. Also certain 

 results follow directly by effect of gravity. Pressure on the abdominal 

 organs, and their varying contents, is exerted upon the great vessels, 

 arterial, venous and lymphatic, the sympathetic plexuses, and the ebb 

 and flow of fluid in them is deranged. Hence function and nutrition 

 of these structures are influenced unfavorably. Man is the only 

 animal which sleeps on the back. This attitude should only be as- 

 sumed for short periods. During extreme weakness this position is 

 often taken, but it is the duty of attendants to urge a frequent change 

 to the side, otherwise several hurtful effects may follow, among which 

 the least grave are nightmare and evil dreams. The poisons of 

 katabolism circulating in the blood tend to be deposited in the outlying 

 tissues ; hence arise pneumonia and bedsores. Not only is this true for 

 those who are suffering from one or another form of disability, but for 

 those in robust health, especially when sleeping on the back after full 

 meals. Many obscure forms of digestive or circulatory disorders 

 may have been initiated in infancy through lying too long upon the 

 back. 



In animals, among whom such disorders are rare and whose spinal 

 column is constantly horizontal, there is little or no change in the rela- 

 tive positions of the great organs at any time. In man, who is con- 

 stantly altering the relationships of these viscera by lying, standing, 

 stooping, the blood supply and venous return are subject to frequent 

 interruptions, and strains are exerted upon the supporting structures 



